Digital rights management comprises a variety of methods, both hardware and software, utilized to control or limit the use of digital content. Such methods are typically used in an attempt to insure that all users of digital content have legitimately purchased the digital content. Such methods may also be used to control or limit software applications.
Software copy protection typically uses one or a combination of the following techniques: a full application can be provided after purchase or registration; a full software application can be activated using a serial number or key; or during installation or when the software is running, an online server can be queried to verify that the installation is legitimate or a registered copy. A problem with providing a full software application only after purchase or registration (either on a disk or via an Internet download) is that a legitimate purchaser can copy the software and provide it to another who could then install and run the software on another device. One problem with activating a full software application using a serial number or key is that a legitimate user can also give this serial number to another who can then activate another copy of the software with the same key. Lastly, a problem with querying an online server to verify whether the installation is legitimate or a registered copy (during installation or when the software is running) is that the program code that executes the online server check can be circumvented to always return a “legitimate” status.
With the advent of “always online” devices, the option of querying an online server has become a popular form of copyright protection. Unfortunately the online server checks can be easily removed or modified. For desktop and mobile device software this poses a serious problem as modified executables are executed by the operating system (OS) with no additional checks or notices. Piracy rates for desktop and mobile device software can be extremely high. For example, the piracy rates of software applications for mobile devices has been reported to be as high as 10:1 when comparing the number of individual software sales to the number of downloads of the software application. Therefore a demand exists for improved methods for controlling digital content and for providing copy protection for software applications.